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Impact Assessment

Ecological Statistics

  1. Allan Stewart-Oaten

Published Online: 15 SEP 2006

DOI: 10.1002/9780470057339.vai002

Encyclopedia of Environmetrics

Encyclopedia of Environmetrics

How to Cite

Stewart-Oaten, A. 2006. Impact Assessment. Encyclopedia of Environmetrics. 2.

Author Information

  1. University of California at Santa Barbara, CA, USA

Publication History

  1. Published Online: 15 SEP 2006

This is not the most recent version of the article. View current version (15 JAN 2013)


A common monitoring problem is: Describe the effect of an environmental alteration on the abundance of a given species at the ‘Impact’ site. Harbors, breakwaters, developments, sewage outfalls, oil platforms, coastal power plants and recreational access – and removals or redesigns of these – are examples in the marine environment, and plants, invertebrates and fish are typical populations of concern. The Impact site is defined naturally in some cases, as a bay or estuary, but arbitrarily in others, as a region surrounding the alteration. Before permitting such alterations, decision makers review predicted effects. These are often subjective, widely varying, and wrong. Monitoring and assessment can aid later decisions: to close the alteration down, modify its design or operation, require mitigation or compensation, allow expansion, or collect further data. By exposing error, it helps keep predictors honest; by adding information, it improves future decisions.


  • p-value;
  • power;
  • effect;
  • intervention;
  • time series;
  • BACI;
  • uncertainty